Split phase off grid RV system

[azozrider]

So I've built and am using a 3kw, 48v LifePo system on a 30A RV. Works great, loving it. But, as life is ever evolving, am finding myself needing to upgrade the size of my Trailer to a much larger one, for new purposes and to accommodate the new family. Which means back to the drawing board for an even bigger system, with more demand on it. I'll of course max out my roof with the highest efficiency panels I can get... probably SunPower Maxeon 6 or Canadian Solar 6sr or whatever those new ones are. Probably do 48v again but might go up again in Voltage to maybe 60v system. Definitely want an all-in-one again, not sure if I will stick with Watts 24/7 and the MPP line or not. Likely up to 310ah lithium (280ah now) cells.

I have to make stupid power, so will find every trick I can come up with to get every inch of collection I can, because I will need to wire in a 240v 40A plug (dryer style) to the garage of the unit in order to power a Photon Genius Super Sauna. Fortunately the thing does use new tech to chop the highs and lows to reduce overall draw like the older versions had, but its still a healthy draw and will run for long periods of time at times. So big power collection, lots of storage, and a generator ignition to help when required, if not plugged into shore, which will happen a lot. Off grid rig. So here is my question....

Will a sufficiently sized (ie LV6048 or bigger) split phase inverter in a 50A RV do the trick for the entire rig, including that 40A plug for Super Sauna, still allowing for Shore charging from whatever is available when something is? If I only have a 20-30A shore outlet and use an adapter on the plug, will one of these split phase converters e the charge? This is predicated on 5-6kw of collection on roof. I've got other 120v heavy draw appliances as well, so will still need to juggle what is on and when. Looking for a little guidance on efficient setup for accomplishing a lot of things.... 240v, 120v, and 12v. 240 and 120v charging. I'll use another converter like I have now for my 12v stuff. Easy.

Thanks!

 

[sunshine_eggo]

How'd that spare cell work out for you?

60V system is likely nothing more than headaches. Full homes run more than adequately on 48V.

Generally speaking, you need to get to know the unit in particular. Some split phase units will work fine if you feed them only 120V on one leg. Others won't work at all. Most will shit their pants if you just plug in with a 30-50A adapter as the adapter shorts the L of the 30A plug to BOTH L1 and L2. You'd likely want a custom adapter that leaves L2 dead on the AC input side to be certain.

If you're going to be pulling bigger loads and running bigger inverters, your idle draw is only going up. The LV6048 burns nearly 100W or 2.4kWh/day meaning your first 500W of PV on the roof is feeding what the inverter consumes.

 

[azozrider]

Hey! That cell has worked well, thanks. She's in storage again now while I'm out of country again for a bit.

Ah, yeah the short of L1 and L2 would be a problem, so I'll have to make a custom adapter for sure.

Shoot, had forgotten to factor idle draw of larger inverter. Definitely gonna have to find a way to easily deploy extra, or do what I had considered on current rig, and fabricate some scissor type arms to fold out more panels when parked. There's a sweet new RV Solar awning with 1000W but they want $10k for it! Just the awning!

Any recommends on an efficient unit that will behave? I'll contact Ian at Watts 24/7 and ask about Growatt and MPP units.

What about paralleling 2 units, like MPP's, and running only 1 until the 240 is needed, then switching the 2nd one on. Is that doable? Because there will be plenty of time that that 240v plug will not need to be run, wasting all that idle time consumption. Especially at night.

 

[sunshine_eggo]

Hey! That cell has worked well, thanks. She's in storage again now while I'm out of country again for a bit.

Glad to hear it.

What about paralleling 2 units, like MPP's, and running only 1 until the 240 is needed, then switching the 2nd one on. Is that doable? Because there will be plenty of time that that 240v plug will not need to be run, wasting all that idle time consumption. Especially at night.

Many units configured to work in parallel tend to object when their buddy is not present. If it does work, then you'll lose the entire L2 leg, not just the 240V. You would also likely want a means of shorting L of the "L1" unit to the L2 half of the panel so everything 120V will work.

If you plan for the idle cost, it's no biggie, but many folks find out at the end of the road that they're consuming 20-50% of their battery capacity in idle draw, and they have a smaller portion of their array "usable" for loads than they thought.

Ian should have some words of wisdom.

 

[azozrider]

Makes sense. I was just gonna write him. One challenge I just discovered in going over specs of the 6048 and paralleled 3048's is the limit on array input. They cite 4kw, and I will be at least 5-6kw... more if I can sort out a way to do it. Leaving me to believe the big Growatt 12kw home unit may be my only option. 200lb unit to mount in an RV! Hmmm. Damn sure won't be anything like this system on the road if I decide to do this! Not sure there anything like what I have already! I'm a sucker for a challenge though.

 

[azozrider]

So kinda back to square one after some emailing with Ian. It sounds as though I will need one or two paralleled units for the 240v appliance, and one 120V unit for the 120V and 12V loads and battery charging? And the 2 or 3 all communicating so that whatever shore or generator power is required and available it can be supplied.

 

[Johneb]

Have you looked at the Samlex EVO 4248SP? It allows for 100a VOC from solar through the unit. I don't know enough about solar to know if this fits your needs. 4200 watt split phase. You could alway add a solar charger direct feed to the batteries for whatever the Inverter/charger won't accept.

 

[azozrider]

No, thats smaller than what I have and totally insufficient for my needs. I‘ll look though at the brand and see if they offer something. I‘ll be collecting 5-6kw minimum. Separate charging and trying to make them communicate effectively is just too complicated for my pea brain. I like simple and effective. But thanks for possible lead on a brand. I‘ll have a look.

 

[Vigo]

Many units configured to work in parallel tend to object when their buddy is not present. If it does work, then you'll lose the entire L2 leg, not just the 240V. You would also likely want a means of shorting L of the "L1" unit to the L2 half of the panel so everything 120V will work.

I remember reading that there is a Victron that does something like this.. i.e. giving split phase under some conditions, and shorting one line to both outputs for 120v during other times. I thought it was odd and didn't look far into it.

It may be preferable to have separate 120 and 240v systems anyway if you don't have any 'continuous' 240v loads and can simply turn on that system when needed. One nice thing about having 2 separate inverters or groups of inverters hooked to the same battery bank is that the side which is 'off' can still charge battery from grid or generator without having to switch the entire load carried by the running inverter(s) to that source.

 

[azozrider]

Good points. Yea the 240v will only be for one appliance and likely nearly always during daylight. I’ll run just the one new circuit for it, with a breaker of course.

Enjoyed Will’s videos on the EG4 units. Fun part will be finding room for all those inverters! Anyone know how loud fans are on the EG4’s?

 

[Rocketman]

What about running an auto transformer (look at Victron) to create the 240v for that one item?

Autotransformer - Victron Energy

Use the Autotransformers for step up, step down and split phase output balancing purposes. Find a Victron Energy dealer near you.

www.victronenergy.com

Stack 120v inverters to get the needed amps.

Probably doesn’t have the capacity you need - but worth a look. (Maybe another brand will make the 40a instead of 32a).

 

[azozrider]

Yeah nowhere near sufficient and at a ridiculous cost. Im sure victron is good… but you’d have to go through a lot of other inverters and batteries before matching the cost. Doesn’t seem worth it.

 

[Vigo]

Yeah, for high power devices it's cheaper to go with a 240 inverter for the 240 load and make a small 120 from a small transformer, than it is to start with gigantic 120 inverters to make a 240 with a gigantic transformer.

Ive got two small autotransformers and ive run them both ways so im very receptive to autotransformer use in general, but that is not a very cost effective way to use them imo.

In general having two large 240 inverters in parallel and an autotransformer to make a smaller 120 supply would be good in this scenario EXCEPT for trying to incorporate grid charging or generator charging. Only certain inverters will 'mix' grid/generator with battery power. My Growatts cannot do it and would instead activate their transfer switches and try to switch the entire load to grid/generator, which is no good in OP's scenario.

That's why i mentioned the possible upside of having separate 120 and 240 inverters powered by the same battery. Even if the shore power or generator couldn't power the whole 240v/40a load, the 120 inverter could still be charging batteries from that input and effectively offsetting the total battery consumption of the 240 inverters. Some inverters may have the right combination of features to provide split phase (120 & 240) AND mix power from the grid AND provide enough total power to supply the need in this case. I don't know which ones that would be. I suspect Victron has it if you want to spend Victron money to get it.

 

[azozrider]

Victron just too far out of range on pricing for most of us mortals. I'd never see the ROI on the system. Ian seemed to indicate 3 MPP's could do the trick. I could hold it to 2 except for the limitation of array input. 2 for the 240v system and 1 for the 120v and shore/gen charging help when required. Guess I'll add it all up and see if the whole thing makes any kind of sense. And all this is before the $28k appliance I'll be running and the mods to a toy hauler to build out the healing studio! But will be cheaper than commercial rent and I don't have to stay put! Debating a 2nd trailer behind the first just as a studio, so I can drop in places. But then the challenge of making enough power off a small trailer. Lotta fiddling around with #'s for sure.

 

[Vigo]

2 for the 240v system and 1 for the 120v and shore/gen charging help when required.

It's nice to make the system out of 120v inverters because then they accept 120v inputs!

It's massively irritating that my Growatts won't 'accept' 120 as a grid input. Because they WILL. But they won't.. It says in the manual they will operate on a ~90-280v input voltage, and there is even a chart specifying how much the inverter will 'derate' when operating on 120, but if you plug 120 to it it will never start using it. But get this.. If you feed it 240 and then rapidly switch it to 120 like AH-HAH! GOT YOU it will then continue operating merrily on that 120v input (charging batts but not powering loads in my case). I have a small cheap PowMR 240v inverter that does the same thing. This is a side effect of them always trying to switch loads over to grid any time it sees 'grid power' (which is just, the ac input). If you had inverters that were capable of mixing grid with battery power they might just do so without requiring that input voltage be the same as output voltage. Speculation in my case because i don't own anything that nice.?

So using 3 120v inverters, or at least 1, is nice because it means you can actually FEED IT 120 without having to 'trick it'.

Another thing you can do with two separate systems is set 1 of them to have X 'charge from shore/gen' limit, and set the other one to have Y limit, put breakers between each one and the AC source, and then pick which charge rate you want based on which one has the breaker on. Or both, even. Or, have one setup for a ~1500w limit from shore, another one set for ~4000w limit from generator, and use both simultaneously etc. Basically if you only had 1 set of parallel inverters you would have multiple ac input terminals but you would likely have only one set of shared 'input settings' which you'd have to manually change through menus every time you used a power source of different capacity, and the units might fault out if their inputs didn't all match. So even if you decided to pull the same power from grid or from generator, and both limits were below the limit of a single inverter, you couldn't just plug each of them to a different inverter's input, you'd have to wire them through an external transfer switch so that all the inverters saw the same thing even if not all the inverters necessarily did anything with it . So having non-paralleled inverters gives you more flexibility for using multiple AC inputs.